1. Field of the Invention
The present invention relates to a vibration damper for use in vehicles, and more particularly to a vibration damper supported on an overhung pin.
2. Description of the Related Art
Recently, more and more vehicles are designed to be smaller in weight, height and engine room space. To catch up with this tendency, the vibration dampers used mainly as the engine mount also show a tendency to be smaller since they are to be installed in such narrower engine rooms. Especially, with the tendency of the engine room space to be narrower, overhung type engine mounts are adopted in more and more vehicles. On the other hand, in the automobile industries, an easier installation of the engine mount between the car body and engine has been considered for an improved productivity. The overhung type engine mounts have so far been proved to be easiest to install. To support a heavy engine, a large overhung pin should be used.
FIG. 1 is a cross section of a conventional overhung type engine mounts, and FIG. 2 is a sectional view, taken along the line Bxe2x80x94B in FIG. 1, of the engine mount. As shown, the conventional overhung type engine mount typically includes inner and outer cylinders 21 and 22, an elastic rubber body 23 formed from an unvulcanized rubber filled between the inner and outer cylinders 21 and 22 and then vulcanized to combine the cylinders with each other, and a pin 24 forced-fitted in the inner cylinder 21. Since the pin 24 has to support the weight of the heavy engine, it has to be large in diameter. The diameter of the inner cylinder 21 in which the pin 24 is force-fitted should be large accordingly.
While the engine mount should preferably have a smaller structure for the above reason, its inner cylinder 21 has to be large in diameter. To meet the former requirement, the elastic rubber body 23 existent between the inner and outer cylinders 21 and 22 has to be smaller in volume and the arm length of the rubber will also be reduced, which has a possibility to reduce a durability of the engine mount. The increased diameter of the inner cylinder 21 is opposite to the requirement for the smaller weight and small size of parts. If the engine mount is designed to be smaller, the arm length of the elastic rubber body 23 has to be reduced correspondingly. Therefore the engine mount is desirable to be designed to be smaller without lower durability.
The present invention has an object to overcome the above-mentioned drawbacks of the prior art by providing an overhung type vibration damper having a new structure.
The above object can be attained by providing a vibration damper including according to the present invention, an outer cylinder, an overhung pin which is put inside the outer cylinder, and an elastic rubber body put between the outer cylinder and overhung pin; the outer cylinder, the overhung pin and the elastic rubber body being combined with each other with an adhesion strength the elastic rubber body will have when it is vulcanized.
In the vibration damper according to the present invention, the outer cylinder forming the shell of the vibration damper and the overhung pin supporting an engine are combined directly with each other by vulcanizing a vibration damping rubber put between the outer cylinder and overhung pin. Thus, the inner cylinder is the conventional vibration damper is omitted in the vibration damper according to the present invention in which thus the free length of the elastic rubber body can be assured even with an increased diameter of the overhung pin. Also, since the inner cylinder is thus omitted, the vibration damper can be smaller in weight and in addition the manufacturing cost of the product can be reduced since the process of force-fitting the pin into the inner cylinder is not required.
The elastic rubber body referred to herein may be an ordinary rubber. To provide a damping effect of the fluid, the elastic rubber body may be a one in which a fluid is sealed.
Note that the present invention is advantageous in that the overhung pin may be a tandem pin which is formed with different diameters. The pin could not be used in the conventional product since the pin has to be force-fitted into the inner cylinder. Namely, the omission of the inner cylinder has thus contributed to the improvement of the vibration damper according to the present invention.
More specifically, the larger diameter at a central portion of the pin in contact with the elastic rubber body than the diameter at opposite ends of the pin, permits to prevent the pin from going out of the elastic rubber body. Further, the waving of a central portion of the pin contributes to increase the area of contact with the elastic rubber body, thus increasing the adhesion strength to the elastic rubber body.
These objects and other objects, features, and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments of the present invention when taken in conjunction with the accompanying drawings. It should be noted that the present invention is not limited to the embodiments but can freely be modified without departing from the scope and spirit thereof defined in the claims given later.